When your children are young, you feel that no matter how loud you shout, or how brilliantly you manipulate them, they're not really listening. Then they grow up and you realise that they've been listening only too closely. You've been a massive influence on them. If only you'd realised it at the time, you'd have behaved better. But you didn't and now it's too late.

Steve Toltz's debut novel, A Fraction of the Whole, takes the form of Martin Dean's confession of his failures and hopes to his son, Jasper. It's a hard book to describe; whoever wrote "rollicking" on the press release, for instance, should buy a dictionary. Dante's Paradiso is more rollicking than this. It's a fat book but very light on its feet, skipping from anecdote, to rant, to reflection, like a stone skimming across a pond.

Toltz is profligate with his stories: any one of Martin's anecdotes would make a decent full-length novel. And not all the same kind of novel either - there's a section about a labyrinth that you could imagine Borges writing, another about a lottery gone wrong that made me think of Vonnegut, and a strange, lovely account of childhood illness that had echoes of García Márquez. In some ways it plays like a modern Arabian Nights, with Martin as Sinbad. His bad-tempered, regretful voice gives the book a unity and immediacy that makes it feel less like a novel and more like a stand-up routine (the book it reminded me of most was Alexei Sayle's brilliant Overtaken). One of the characters, for instance, writes a kind of Do It Yourself guide for aspiring criminals that includes such chapter titles as "Motiveless Crime: Why", "Armed Robbery: Laughing all the way from the bank" and "Manslaughter: Ooops!". Or how about this - "There were no two ways about it: I was in a crisis. But recent shifts in the behaviour of different age groups made it hard to know what type - How could it be a midlife crisis when the forties were the new twenties, the fifties the new thirties . . . I had to read the lifestyle supplement to make sure I wasn't going through puberty."

Just as Jasper's life is overshadowed by his father's, so Martin's is overshadowed by that of his brother, the criminal genius Terry Dean, who uses a spell in prison to start up a kind of criminal cooperative ("the state is always going about the business of introducing dangerous criminals to each other - they plunge them right into the network"). From childhood, when Terry was a sporting hero, through adulthood when he becomes Australia's most notorious killer, Martin is only ever "Terry's brother". Even the woman he loves only comes to him in the absence of his brother. In the end, Martin is able to achieve his own identity only by committing a worse crime than his brother's.

I'm sorry if I'm beginning to make it sound a bit rollicking. The stories, in fact, follow a pattern: they are almost all tales of good intentions with catastrophic results, such as the suggestion box which Martin installs on the town-hall steps and which at first instils a new sense of purpose and confidence in the community, but quickly brings out the worst in everyone and leads to his brother being sectioned. Taken individually, they're funny; taken together, the unbreakability of the pattern and the inevitability of disaster is heartbreaking.

This is only emphasised by the fact that, despite the size and scope of the book, there are very few characters in it. The same people keep popping up in the most unlikely places, like watching a lot of Road Runner cartoons one after the other: the more you admire the inventiveness and hope of Wile E Coyote, the more you can't bear to look as he plunges off the edge of the canyon. Fools ask why the Coyote is so fixated on Road Runner. Haven't they noticed that in all the wide desert there's nothing else moving? In all our lives, no matter how far we roam, how much we achieve, we were only ever after the attention and approval of a very small number of people - our parents, our children, our lovers.